The ability to achieve superconductivity using liquid nitrogen cooling in copper oxide superconductors has excited scientists trying to develop these ceramics into useful form. Although great efforts have been expended in the last few years, unfortunately, owing to chemical and thermal instabilities of these copper oxides, materials of the required quality have not yet been achieved. It has been apparent that other approaches to the synthesis of these materials must consider their instabilities. The instabilities include phase stability, oxide volatility and the instability of the copper oxidation state at high temperature.
Significant progress has been made toward solution of the instabilities by using alkaline hydroxide as a low temperature flux. For example, in U.S. Pat. No. 5, 256, 260 issued to Michael L. Norton and the co-inventor of this application, Horng-Yi Tang, there is disclosed an electrodeposition method which can synthesize crystalline Ba--K--Bi--O layers on anode with 32K as-grown superconductivity under isothermal, constant potential conditions using a three-electrode, one-compartment cell geometry operating at a temperature of 260.degree. C. However, the poorly defined phase diagram and complexity of flux-complex ions interactions limit this low temperature method in binary and a few ternary oxides systems which can not have transition temperature higher than the liquid nitrogen region.